Nokia on Monday unveiled the Lumia 900, its first 4G LTE phone, which will run over the AT&T network.

Nokia CEO Stephen Elop introduced the Windows Phone 7.5 (Mango) device at a press conference at CES, where he was joined by Microsoft CEO Steve Ballmer.

The Lumia 900 will follow Nokia's first Windows Phone, the Lumia 710 , which will run on T-Mobile USA within a matter of days for $49.99 after rebate and a two-year contract.

"We have a lot of room to go in terms of selling Windows phones," Ballmer said, but he noted that AT&T is already the biggest Windows Phone carrier in the U.S. Windows Phone has less than 3% of the smartphone market, well behind Apple 's iPhone and various Android devices.

AT&T Mobility's CEO Ralph de la Vega joined Elop and Ballmer in the announcement. "Believe me, I think Nokia is going to be back in the U.S. in a very big way," de la Vega said.

"This phone is truly built around people and not applications." The Lumia 900 will ship in coming weeks, he said.

Nokia emphasized high-quality front and rear-facing cameras in the Lumia 900, but otherwise discussed few details.

Prior to the announcement, various blogs said the phone would have a 4.3-in. screen and one 8-megapixel camera. The phone has a 1.4 GHz Snapdragon processor, an 1830 mAh battery and 16GB of internal storage .